12.2.1 - Acid-base titrations, pH curves and indicators

Question 1

What is the end point of a titration?

Answer 1

The point at which the indicator used in the titration changes colour.

Question 2

What is the equivalence point of a titration?

Answer 2

When the acid and base have reacted together in exact proportions as dictated by the stoichiometric equation.

Question 3

For a strong acid-strong base reaction where the acid is being added, what does the pH start and end at?
What is the equivalence point?

Answer 3

Starts at 14
Ends at roughly 1

7

Question 4

For a weak acid-strong base reaction where the acid is being added, what does the pH start and end at?
What is the equivalence point?

Answer 4

Starts at 14
End at 3/4

8.5

Question 5

For a strong acid-weak base reaction where the acid is being added, what does the pH start and end at?
What is the equivalence point?

Answer 5

Starts at 11
Ends at about 1 or 0.5

5.5

Question 6

For a weak acid-weak base reaction where the acid is being added, what does the pH start and end at?
What is the equivalence point?

Answer 6

Starts at 11
End at 3/4

7

Question 7

What is significant about the graph of an weak acid-weak base raction?

Answer 7

There is no equivalence point, instead there is a point of inflection

Question 8

What are most acid-base indicators?

Answer 8

Weak acids

Question 9

How do you know what the best indicator is for a reaction?

Answer 9

The one with PKin value closest to pH at equivalence point.

Question 10

What is the pH range of phenolphalein?

Answer 10

8.20 - 10.00

Question 11

What is the pH range of methyl orange?

Answer 11

3.10 - 4.40

Question 12

For the 4 different acid-base reactions describe which of the two indicators methyl orange and phenolphalein would work?

Answer 12

Strong acid - strong base = both
Weak acid - strong base = Only phenolphalein
Strong acid - weak base = Only methyl orange
Weak acid - Weak base = Neither